Added an amp...now spkr hum?

[mnnc]

Added a power amp to the rig and now I have a slight hum coming from speakers. Any idea as to why? Cables are jumbled together behind rack crossing each other but they were that way before when just the recv'r was being used w/o the new amp and I had no noise. Amp does have a ground screw/knob. Any suggestions. Speaker wires are not touching each other at connection point. I don't want to damage anything. Thank you.

 

[j_garcia]

Try running a ground wire from the amp to the ground on the receiver.

 

[majorloser]

The Dreaded Ground Loop Hum

More than likely you have the dreaded "ground loop" problem

Don't worry there is plenty to read on this site about it. Just read the articles and try the recommended fixes. It's not hard but can take a little time to work through the problem. It can be something as easy as grounding the amp to the receiver chassis by running a wire from the amp ground screw to a screw on the external of the receiver. Sometimes receivers have a ground screw that is used with the phone input.

Here's a little reading to keep you busy:

http://www.audioholics.com/tweaks/connecting-your-system/ground-loops-eliminating-system-hum-and-buzz/?searchterm=ground loop

http://www.audioholics.com/education/cables/thinking-in-isolation-2013-a-primer-on-ground-loops/?searchterm=ground loop

http://www.audioholics.com/education/cables/balanced-vs-unbalanced-interconnects/?searchterm=ground loop

 

[mnnc]

More than likely you have the dreaded "ground loop" problem

Don't worry there is plenty to read on this site about it. Just read the articles and try the recommended fixes. It's not hard but can take a little time to work through the problem. It can be something as easy as grounding the amp to the receiver chassis by running a wire from the amp ground screw to a screw on the external of the receiver. Sometimes receivers have a ground screw that is used with the phone input.

Here's a little reading to keep you busy:

http://www.audioholics.com/tweaks/connecting-your-system/ground-loops-eliminating-system-hum-and-buzz/?searchterm=ground loop

http://www.audioholics.com/education/cables/thinking-in-isolation-2013-a-primer-on-ground-loops/?searchterm=ground loop

http://www.audioholics.com/education/cables/balanced-vs-unbalanced-interconnects/?searchterm=ground loop

Well, tried the gnd from amp to recvr's phono gnd. Nothing. Switched source inputs via recv'r(now pre/pro) and no difference. Then I started wiggling(more like moving left,right, up, down) the rca's that connect amp to recv'r. The volume of hum would increase/decrease slightly as they were moved. Had my son listen while I moved them around a bit and we switched turns and I listened. There is a difference in the hum level when the interconnect is moved around. The hum never cuts out which would indicate a bad/broken cable but simply increases/decreases hum level. The rca's are basic sherwood units that were supplied w/ amp. Purchased amp from very reputable seller on agon. Sounds great and channels come through/work. Think I need better shielded cables? Or simply try to isolate them from other cables? Thank you for the help. You can't imagine how much this bothers/worries me.

 

[j_garcia]

Shielding isn't the issue, but the cables would be my next choice. Read the third article, as it sounds like this may be the culprit if a ground wire did not solve it:

This coupling is referred to as common-impedance coupling , and is the result of the fact that in an unbalanced two-wire system the shield is performing two functions. It is a shield carrying the common-mode noise current, but it is also one of the signal conductors carrying the return signal current.

All my analog cables are "balanced" in so far as a standard RCA can be considered as such (separate ground wire rather than using the shield).

 

[mjhamre]

I'm going through EXACTLY the same thing, posted on it a while back with some of the same set of suggestions coming up. I did not see an obvious ground screw on the amp, so I have not tried that, but I did do a ton of testing last weekend to try to narrow down the problem.

Unplugged everything from the wall, all power cables, cable line, everything. Left the components all connected to each other as usual, because damn that is a lot of components. Started plugging things in, amp, receiver, no problems. Eventually plugged in a wall wart for a crappy under monitor dell speaker, hum started (softly). Moved that to a different outlet, fixed the hum, easy to do. Plugged in cable line, hum started (softly). Added recommended isolator from parts express ($10 I think, pretty sure I read about in one of the links that was passed on to you) hum went away.

At that point I thought I was set, streamed music from the PC, no problem. Then turned on TV and hum and buzz was really impressive, heard it during quiet times from the listening position (the rest of the above was put your head near the speaker kind of stuff). Turned the TV off, no problem. Made sure all cables going to/from TV were no where near speaker wires, made sure TV power cable was no where near component cable going to TV, still buzzing and humming. Ran a 25 foot extension cord to the kitchen and turned on the TV, no buzz, no hum.

I had to stop to watch the NCAA tournament at a friend's house, and have not gotten back to it yet, but I need to:
1) Ground the amp and receiver as suggested to see if that helps. Since turning the TV on and off is a controlled thing that totally screws up the system, I'm not sure how the ground between the amp and receiver is getting out of whack, if anyone has ideas, please post or PM me.
2) Unplug the component cable from the TV and see if turning it on and off still affects things. That should say whether signal is leaking back to the receiver through the component lines or the way the TV is using the power line is causing a problem.

I purchased the amp because I am moving to a house with a very large open floor plan and figured my $500 4 year old Yamaha could probably use some help with the front three channels. Like you said, finding this buzz and hum has not been fun. Maybe something in my description will help, and I will definitely follow up this weekend when I do some more testing. Please be sure to post if you find a solution (which I suppose I should do in my thread as well if I ever do get this figured out).

--Matt

 

[mnnc]

I have gone even further by seperating all power cables to one side and plugging all of them into same old filter/surge deal(monster). Still had hum. I then unplugged the rca's from amp inputs so that amp alone with spkr's connected were the only things connected. Still hum. That means hum is coming directly from power amp via spkr cables and ultimately through the spkrs. Amp has 2 prong pwr cord. All 5 spkr's are getting the hum noise. Hhummm? no pun intended. What do I do now?

 

[mjhamre]

I have gone even further by seperating all power cables to one side and plugging all of them into same old filter/surge deal(monster). Still had hum. I then unplugged the rca's from amp inputs so that amp alone with spkr's connected were the only things connected. Still hum. That means hum is coming directly from power amp via spkr cables and ultimately through the spkrs. Hhummm? no pun intended. What do I do now?

One thing I forgot to mention before was that in my case if the TV was turned on when plugged into any outlet on the same circuit the hum was there. Granted that was with a connection (component) to the amp, but there certainly is not supposed to be feedback there. At any rate, as a test it might be worth trying to be sure nothing else on that circuit is turned on. I've heard people who had dimmer switches on lights that were on causing a hum, so maybe something like that. You could also try just using a different circuit by moving the receiver and amp to a different room that you know is on a different breaker...

Good luck.
--Matt

 

[mnnc]

One thing I forgot to mention before was that in my case if the TV was turned on when plugged into any outlet on the same circuit the hum was there. Granted that was with a connection (component) to the amp, but there certainly is not supposed to be feedback there. At any rate, as a test it might be worth trying to be sure nothing else on that circuit is turned on. I've heard people who had dimmer switches on lights that were on causing a hum, so maybe something like that. You could also try just using a different circuit by moving the receiver and amp to a different room that you know is on a different breaker...

Good luck.
--Matt

I did think of that. No other 'things' are turned on in the room other than amp. Tv/lcd is plugged in on standby but not on. Sat box is not on. Again, things plugged in are not powered on. I have a dimmer switch that controls a ceiling wire but it is not on either. I'm going to try a diff outlet. I first have to go jump on the soloflex and do a few curls or something to get warmed up. Damn amp weighs nearly 80lbs. Bought the BA 7200(Sherwood clone) I'll keep this post going until I fix it. I'm determined!

 

[j_garcia]

Does the amp have a gain (volume) adjustment? What do you have it set at? I would agree with trying a few different outlets (verify they are on a different circuit) and see if the hum goes away because you should not have hum with no source connected to the amp.

 

[mnnc]

Does the amp have a gain (volume) adjustment? What do you have it set at? I would agree with trying a few different outlets (verify they are on a different circuit) and see if the hum goes away because you should not have hum with no source connected to the amp.

No gain on pwr amp. Just rcs in's and spkr termz. As I mentioned earlier, I disconnnected the rca's and still got hum. It is a very slight hum that is audible only when you put ear close/next to mid/twtr area. Does not change w/ volume via pre/pro. I'm going to try a diff outlet and post results here in a little while. Amp is silent as far as I can tell putting my ear right next to it. Thanks for help/interest.

 

[wire]

No gain on pwr amp. Just rcs in's and spkr termz. As I mentioned earlier, I disconnnected the rca's and still got hum. It is a very slight hum that is audible only when you put ear close/next to mid/twtr area. Does not change w/ volume via pre/pro. I'm going to try a diff outlet and post results here in a little while. Amp is silent as far as I can tell putting my ear right next to it. Thanks for help/interest.

Is this amp brand new ?

 

[mnnc]

Is this amp brand new ?

No. pre-owned. Purchased from reputable agon member. Guy deals w/ much higher end stuff than this amp and perfect fb on his part. Nonetheless, I just switched outlets and still the 'static' sound. I suppose it is more Static than Hum. As I write the amp is powered on with spkrs connected and all 5 have this slight static coming from them. Not audible once I send signal through system. No recv'r on or connected equip at this moment...just pwr amp and spkr's. Maybe we are having 'bad' power today here in NC. Been 80+F and now we have deep freeze warning for next two nights. Who knows. Circuit I tried is in same room/living rm. Maybe I'll move it to another room and hook up a bookshelf that I have laying around just to test run it.

Let's focus on difference between hum and static. I'm not an acoustic engineer or anything like that but I believe what I hear is static buzz like sound. I must be standing in front of spkr to detect it and put ear next to drivers to really tell where it is coming from. The amp does have dual transformers/lots of current on hand. I have listened to music and watched a couple movies w/ it. It only gets warm, not hot, at operating temp. It does not break a sweat at normal volumes(-30's-20's). Normal by sane means. I guess now the question is when should I be concerned w/ something going wrong? Frying something? Perhaps this is normal. I've narrowed it down to all but conecting to a totally different outlet. I hate to move this thing. I feel it is still going to have the same static even hooked to a diff outlet. Can I use a heavy commercial/contractor ext cord to run it to another outlet?

 

[cliffd]

Try moving the power amp away from your other components. I seperated my ATI amp from my Sunfire preamp by 7" and eliminated the hum

 

[mnnc]

7 in. or 7ft? my amp and recv'r are seperated by about 4 ft. Recv'r on top of rack and amp on bottom. Sub is about 2 ft from amp. Left front speaker is about 2 ft away as well. Left front is powered tower as is the RF. So I have sub and LF next to amp. A lot of magnet going on but they are shielded units. Perhaps interference is going on. Hell, only way to tell is put amp out in the middle of room and try. What's weird is that nothing but spkr's are connected to amp right now and still the static even though it is low level.

 

[j_garcia]

Another outlet won't solve the problem if the noise is coming from the circuit itself. Disconnecting it from the amp completely would tend to suggest there is either something on the power circtuit or there is something wrong with the amp. I have 3 external amps in my system with no noise from them so for future reference I am interested in what happens here in case I run into something like this down the road.

 

[mjhamre]

I've narrowed it down to all but conecting to a totally different outlet. I hate to move this thing. I feel it is still going to have the same static even hooked to a diff outlet. Can I use a heavy commercial/contractor ext cord to run it to another outlet?

With my plasma that when turned on causes what I would call a buzz from the tweeter and more of a hum from the woofers, plugging the plasma into a heavy duty outdoor extension cord and running that to a different room on a different circuit worked well enough to test with. That was how I tested turning it on and not hearing a buzz through the amp and speakers, as I certainly did not feel like moving the plasma.

I know people who are really into it buy special power cords for their components, but I would tend to guess that the consensus here would be that for testing a problem like this a heavy duty extension cord would be fine. A lot easier than moving a 90lb amp and speakers around and if the static/hum/buzz goes away you will have one more piece of the puzzle.

--Matt

 

[mnnc]

I took the time to eat and walk away from it for a while. Got to thinking maybe the spkr connectors. Checked them and even switched ends from flexi ends to banana plugs(just one speaker cable)...same hum/buzz. I even disconnected pwr amp and connected a speaker cable back to the recvr alone and no buzz at all. Remember now, the buzz is coming from power amp with nothing else connected...Nothing. Buzz straight from pwr amp to spkrs OR anytime the pwr amp is connected in the rig. What was strange is that I connected the recvr, pwr amp, and dvd player back in to the rig and played with the volume with no signal going through. Then I played a cd and played w/ volume. When I stopped cd from playing I could hear the buzz. No louder or softer than when I had only the amp/spkr connected. Adjusting volume has no effect on buzz level. Then while cd was not playing I turned volume all the way down and heard a sudden drop in the buzz when volume reached it's lowest point(-70...no volume). Like it cut out. But not all the way. I confirmed this by pressing play...raising volume...listening to a few seconds of music...pressing stop...listened for hum. There it was. Then, like before with cd stopped, I lowered volume all the way down and the buzz again dropped in level. I don't know what the h e double toothpicks the problem is but the amp sounds so good I am just going to play the crap out of it and hope I don't see smoke. This has me confused and ticked off a bit. Maybe with the sub and powered tower spkr so close to amp that they are interfering w/ something? Amp has double huge transaformers right up front.

 

[j_garcia]

I would send it back (contact the seller and let them know what you've done so far), it sounds like it is defective and/or something inside it is failing. The simple fact that it makes noise when nothing is connected to it would suggest this.

 

[davidtwotrees]

Have you tried a ground loop isolator? I was experiencing a hum, and putting the isolator in my cable tv's cable eliminated it lickety split!

Radio Shack didn't have the type that screwed into the cable, so I ordered it off of Parts Express...........